The invention concerns a wheel for a motor vehicle and a process for producing the wheel made of a light metal and produced in a casting process comprising a residual core made of a metallic material and arranged in at least one hollow space of the wheel.
In German Patent Document DE 197 54 959.4, a vehicle wheel is described, which has hollow spaces for weight reduction in which residual cores are arranged. These are placed into the molding tool and encapsulated in casting material. These cores are made either of a metallic foam covered with a skin or of a hollow closed shell. A motor vehicle wheel is also known from German Utility Document DE 297 23 749 U1, which is filled with metallic foam to form a wheel spoke, which is arranged exposing the inner side of the rim spider. Other hollow spaces of the wheel are provided with a residual core of metallic foam, wherefore also the outwardly open metallic foam is arranged in the wheel spoke.
It is an object of the invention to create a vehicle wheel, in particular a vehicle wheel with hollow spokes, which can be produced in a simple manner and has a low weight with an optimal stability.
This object is attained according to the invention via the core being arranged in an area of a rim edge of the wheel in an annular space which is formed by a rim and a rim spider and is open at one side. Other advantageous features are contained in preferred embodiments.
The main advantages obtained with the invention are that the closed hollow spaces as well as the open hollow spaces of the wheel are produced with a residual core. In this way, the core is arranged in the area of a rim edge of the wheel in an annular space open toward one side formed by the rim and a rim spider. For this purpose, according to the invention, a molding tool with sliders is used, which are removably arranged close together in connection to a lower mold. The first slider lying directly beside the lower mold has a recess for a core part, which projects out of the annular space. The second slider seals closed this recess and the annular space.
In this way, it is possible in a simple manner to arrange the core in the annular space of the rim edge so that, after a mechanical processing, a stable rim edge is produced. At the same time, also a casting that can be rolled out to form a rim edge can be produced in the molding tool, which, however, is not absolutely necessary. Rather, also a xe2x80x9creadyxe2x80x9d rim in its final condition can be produced in the molding tool.
According to the invention, the core can be used in the hollow spaces of a rim with or without hollow spokes. The relevant hollow spaces of the wheel in the area of the hub, in the wheel spoke, as well as in the area of the horn can be provided either all or also only part with a core. Therefore, in a wheel with hollow spokes, the core is necessarily provided in the area of the hub, in the hollow spoke, as well as in the area of the horn, since this makes necessary the fixing in the mold. In a wheel without hollow spokes, it is optionally possible to provide the residual hollow spaces with residual cores.
So that an easy processing of the core printsxe2x80x94which hold the core in the molding toolxe2x80x94becomes possible, the core prints are directed toward the outer design of the wheel. The core prints can also consist of several metal pins, which are arranged distributed and projecting with respect to the surface of the core and form a core layer like a pincushion.
The core in the rim edge has at least one core print, which forms a bored-through receiving bore for a wheel valve and in this way saves one processing work step.
The core can have a contoured or rough surface to improve the form-tight connection with the casting material.
The core can be made of a metallic foam with a surrounding layer or skin or can consist of a metallic or ceramic closed hollow body.
According to the invention, the hollow body can consist of one or several pieces and can be produced through a forming process. The materials of which the hollow bodies can be made are ceramic materials, aluminum alloys, or steel alloys. The hollow body can also be filled with foamable metal to obtain an optimal stability of the hollow body.
The metallic foam body can be made, for example, of an aluminum foam, which is protected against the influences of the casting melt during the casting process. This protective layer can be produced via an oxidation process (anodizing) or via ceramic or spray-coating or immersion or spray coating with adhesive materials.
According to another embodiment of the invention, the wheel can also be made completely of plastic, wherein the hollow spaces are provided with residual cores like in a wheel made of metal.
To provide the wheel produced in the casting process with local reinforcements, metallic or ceramic long fiber elements are arranged at the core or the mold, which are encapsulated.